Vacuum servo apparatus

Abstract

A vacuum servo apparatus capable of regulating the output accompanying the activation of an actuator to the maximum output or less includes a housing, movable walls located within the housing, a power piston, an input member, a valve mechanism, an output rod, a reaction disc and an actuator. A rear member forming part of an input member is able to move forward by a predetermined stroke with respect to a front member forming part of the input member so that the input member can be moved backward by the reaction disc in accordance with the activation of the actuator to cut off communication between rear chambers and the atmosphere.

What is claimed is:  
     
       1. A vacuum servo apparatus comprising: 
       a housing having at least one pressure chamber formed therein;  
       a movable wall disposed in said housing to be movable forward and backward with respect to said housing and partitioning said pressure chamber into a front chamber communicating with a negative pressure source and a rear chamber selectively communicated with said front chamber and the atmosphere;  
       a power piston joined to said movable wall;  
       an input member arranged in said power piston to be movable forward and backward with respect to said power piston, said input member including a front member and a rear member separated by a clearance and movable with respect to one another to cancel said clearance;  
       an atmospheric valve seat arranged in said power piston to be movable forward and backward integrally with said rear member of said input member;  
       a vacuum valve seat arranged in said power piston;  
       a control valve including: an atmospheric seal portion adapted to move into and out of abutment against said atmospheric valve seat for cutting off communication of said rear chamber with the atmosphere when the atmospheric seal portion comes into abutment against said atmospheric valve seat and for establishing communication of said rear chamber with the atmosphere when the atmospheric seal portion moves out of abutment against said atmospheric valve seat; and a vacuum seal portion adapted to move into and out of abutment against said vacuum valve seat for cutting off communication between said front chamber and said rear chamber when the vacuum seal portion comes into abutment against said vacuum valve seat and for establishing communication of said rear chamber with said front chamber when the vacuum seal portion moves out of abutment against said vacuum valve seat;  
       an output member for outputting to outside the apparatus a forward force of said power piston in accordance with a movement of said movable wall; and  
       an actuator for moving said atmospheric valve seat and said atmospheric seal portion away from each other to establish communication between said rear chamber and the atmosphere,  
       wherein a predetermined input force applied to said input member during inactivation of said actuator produces an output force from said output member that increases to a predetermined output force, and an output force generated during activation of said actuator is controlled to be smaller than said predetermined output force.  
     
     
       2. A vacuum servo apparatus according to  claim 1 , further comprising: 
       a reaction member for transmitting a forward force of said power piston and an input force fed to said input member, to said output member and for applying a reaction force of a magnitude corresponding to an output force of said output member, to move said input member backward, and said atmospheric valve seat and said atmospheric seal portion can come into abutment against each other to cut off the communication between said rear chamber and the atmosphere when said input member is moved backward by a reaction force of said reaction member in accordance with the activation of said actuator.  
     
     
       3. A vacuum servo apparatus comprising: 
       a housing in which is provided at least one pressure chamber;  
       a movable wall disposed in the housing and partitioning said pressure chamber into a front chamber communicating with a negative pressure source and a rear chamber selectively communicated with said front chamber and the atmosphere;  
       a power piston joined to said movable wall to produce a forward force;  
       an input member arranged in said power piston for forward and backward movement with respect to the power piston and adapted to be connected to a brake pedal;  
       a valve mechanism for selectively establishing a first state in which the rear chamber is in communication with the front chamber and is prevented from communicating with the atmosphere and a second state in which the rear chamber is prevented from communicating with the front chamber and is in communication with the atmosphere to create a pressure differential between the rear chamber and the front chamber which moves the movable wall;  
       an output member for outputting to outside the apparatus a forward force of said power piston in accordance with movement of said movable wall; and  
       an electrically operable actuator for bringing said valve mechanism into said second state during operation of the actuator, the apparatus producing a jumping output during operation of the actuator that is less than the jumping output produced during inactivation of the actuator when a force is applied to the input member as a result of operation of the brake pedal.  
     
     
       4. The vacuum servo apparatus according to  claim 3 , wherein the input member includes a front member and a rear member that are separated from one another by a clearance, the rear member moving forward relative to the front member to cancel said clearance during inactivation of the actuator when a force is applied to the input member as a result of operation of the brake pedal, and said front member moving backward during operation of the actuator. 
     
     
       5. The vacuum servo apparatus according to  claim 4 , including a reaction member for transmitting the forward force of said power piston and an input force applied to said input member to said output member and for applying a reaction force of a magnitude corresponding to an output force of said output member to move said input member backward. 
     
     
       6. The vacuum servo apparatus according to  claim 4 , wherein one of the front and rear members includes a longitudinally extending hole that is closed at one end and the other of the front and rear members includes a longitudinally extending engaging protrusion that fits within the longitudinally extending hole. 
     
     
       7. A vacuum servo apparatus comprising: 
       an operational member for receiving an input force;  
       a first output force generator operatively associated with said operational member for generating a first jumping output in response to operation of said operational member; and  
       a second output force generator operable independently of operation of said operational member for generating a second jumping output that is less than the first jumping output.  
     
     
       8. The vacuum servo apparatus according to  claim 7 , wherein the first output force generator includes an input rod connected to the operational member for forward and backward movement, an input member connected to the input rod, an output rod for outputting the first and second jumping forces, and a reaction member for applying a reaction force of the output rod to move the input member backward, the input member including a front member and a rear member, with a clearance being provided between the front and rear members, said rear member moving forward during operation of said operating member to cancel said clearance and said front member moving backward during operation of said second output force generator. 
     
     
       9. The vacuum servo apparatus according to  claim 8 , wherein one of the front and rear members includes a longitudinally extending hole that is closed at one end and the other of the front and rear members includes a longitudinally extending engaging protrusion that fits within the longitudinally extending hole. 
     
     
       10. The vacuum servo apparatus according to  claim 7 , wherein the first output force generator also includes a housing in which is provided at least one pressure chamber, a movable wall disposed in the housing and partitioning the pressure chamber into a front chamber communicating with a negative pressure source and a rear chamber selectively communicated with the front chamber and the atmosphere, a power piston joined to the movable wall to produce a forward force, and a valve mechanism for selectively establishing a first state in which the rear chamber is in communication with the front chamber and is prevented from communicating with the atmosphere and a second state in which the rear chamber is prevented from communicating with the front chamber and is in communication with the atmosphere to create a pressure differential between the rear chamber and the front chamber which moves the movable wall. 
     
     
       11. The vacuum servo apparatus according to  claim 7 , wherein the second output force generator includes an electrically operable actuator. 
     
     
       12. A vacuum servo apparatus comprising: 
       a housing having at least one pressure chamber formed therein;  
       a movable wall disposed in the housing to be movable forward and backward with respect to said housing and partitioning said pressure chamber into a front chamber communicating with a negative pressure source and a rear chamber selectively communicated with said front chamber and the atmosphere;  
       a power piston joined to said movable wall;  
       an input member arranged in said power piston to be movable forward and backward with respect to said power piston;  
       an atmospheric valve seat arranged in said power piston to be movable forward and backward integrally with said input member;  
       a vacuum valve seat arranged in said power piston;  
       a control valve including: an atmospheric seal portion adapted to move into and out of abutment against said atmospheric valve seat for cutting off communication between said rear chamber and the atmosphere when the atmospheric seal portion comes into abutment against said atmospheric valve seat and for establishing communication of said rear chamber with the atmosphere when the atmospheric seal portion moves out of abutment against said atmospheric valve seat; and a vacuum seal portion adapted to move into and out of abutment against said vacuum valve seat for cutting off communication between said front chamber and said rear chamber when the vacuum seal portion comes into abutment against said vacuum valve seat and for establishing communication of said rear chamber with said front chamber when the vacuum seal portion moves out of abutment against said vacuum valve seat;  
       an output member for outputting to outside the apparatus a forward force of said power piston in accordance with a movement of said movable wall;  
       a reaction member for transmitting the forward force of said power piston and an input force fed to said input member to said output member and for applying a reaction force of a magnitude corresponding to an output force of said output member to move said input member backward; and  
       an actuator for bringing said atmospheric valve seat and said atmospheric seal portion away from each other to establish communication between said rear chamber and the atmosphere,  
       wherein said input member includes: a front member for coming into abutment against said reaction member; and a rear member separated from said front member by a clearance and capable of moving integrally with said atmospheric valve seat, so that when a first predetermined input force is fed to said input member, said rear member moves forward by predetermined stroke with respect to said front member so as to cancel said clearance, and so that when said front member and said rear member are integrally moved backward by a reaction of said reaction member in accordance with the activation of said actuator, said atmospheric valve seat and said atmospheric seal portion can come into abutment against each other to cut off the communication between said rear chamber and the atmosphere.  
     
     
       13. A vacuum servo apparatus according to  claim 12 , wherein said input member and said reaction member are in abutment against each other in an initial state where no input force is applied to said input member. 
     
     
       14. A vacuum servo apparatus according to  claim 12 , wherein said front member is joined to said rear member by a pin provided on one of the front and rear members that is fitted into an elongated slit in the other of the front and rear members so that when said rear member moves forward by the predetermined stroke with respect to said front member said front member and said rear member may integrally move forward. 
     
     
       15. A vacuum servo apparatus according to  claim 14 , including a longitudinally extending recess arranged in one of said front member and said rear member that is closed off at least at one side end portion thereof and an engaging portion formed on the other of said front and rear members and inserted into said recess to move longitudinally. 
     
     
       16. A vacuum servo apparatus according to  claim 12 , further comprising: 
       a first bias member for biasing said rear member backward.  
     
     
       17. A vacuum servo apparatus according to  claim 12 , further comprising: 
       a second bias member arranged between said front member and said rear member for biasing said rear member backward with respect to said front member.  
     
     
       18. A vacuum servo apparatus according to  claim 12 , wherein one of said front member and said rear member includes a longitudinally extending engaging protrusion and the other of said front member and said rear member includes a longitudinally extending assembly hole that slidably receives said engaging protrusion. 
     
     
       19. A vacuum servo apparatus according to  claim 12 , further comprising: an engaging member elastically deformed when said input member is moved backward by the reaction force of said reaction member in accordance with the activation of said actuator for allowing the backward movement of said input member. 
     
     
       20. A vacuum servo apparatus according to  claim 19 , wherein said engaging member engages with said input member in accordance with the forward movement of said power piston with respect to said input member by the activation of said actuator to enable said input member and said atmospheric valve seat to move integrally with said power piston. 
     
     
       21. A vacuum servo apparatus according to  claim 19 , wherein said engaging member engages with said input member when said actuator is activated during inactivation of said input member to move said power piston forward with respect to said input member, so that said input member is moved backward by the reaction force of said reaction member against a restoring force accompanying an elastic deformation of said engaging member in accordance with the activation of said actuator during inactivation of said input member, which enables to bring said atmospheric valve seat and said atmospheric seal portion into abutment thereby to cut off communication between said rear chamber and the atmosphere. 
     
     
       22. A vacuum servo apparatus according to  claim 19 , 
       wherein said engaging member is a key member engaging with said power piston for moving longitudinally by a first predetermined stroke with respect to said power piston and with said input member for moving longitudinally by a second predetermined stroke with respect to said input member,  
       wherein said housing includes a first opposed portion opposed to and adapted to abut against a rear face of said key member,  
       wherein said power piston includes: a second opposed portion opposed to and adapted to abut against a front face of said key member; and a third opposed portion opposed to and adapted to abut against the rear face of said key member, and  
       wherein said input member includes: a fourth opposed portion opposed to and adapted to abut against the front face of said key member; and a fifth opposed portion opposed to and adapted to abut against the rear face of said key member.  
     
     
       23. A vacuum servo apparatus according to  claim 12 , further comprising: 
       a valve seat member arranged to move forward and backward with respect to said power piston independently of the movements of said input member and adapted to abut against said vacuum seal portion of said control valve for cutting off the communication between said front chamber and said rear chamber,  
       wherein said rear member of said input member is integrally equipped with said atmospheric valve seat, and  
       wherein said actuator moves said valve seat member backward to bring said valve seat member into abutment against said vacuum seal portion and moves said vacuum seal portion backward to bring said atmospheric seal portion apart from said atmospheric valve seat thereby to establish the communication between said rear chamber and the atmosphere.  
     
     
       24. A vacuum servo apparatus according to  claim 23 , wherein a drive force of said actuator is adjustable to adjust the output force from said output member. 
     
     
       25. A vacuum servo apparatus according to  claim 24 , wherein the drive force of said actuator is adjustable to adjust a backward movement of said valve seat member with respect to said power piston. 
     
     
       26. A vacuum servo apparatus according to  claim 23 , 
       wherein said actuator includes a solenoid connected with an electric power source for attracting and moving said valve seat member backward when said solenoid receives an electric power, so that the output force from said output member can be adjusted according to an attraction force of said solenoid.  
     
     
       27. A vacuum servo apparatus according to  claim 26 , 
       wherein said valve seat member is adjusted in the backward movement thereof in accordance with the attraction force of said solenoid.  
     
     
       28. A vacuum servo apparatus according to  claim 23 , further comprising: 
       a third bias member arranged between said valve seat member and said power piston for biasing said valve seat member forward.